The general base line solution to spectrometers is Ocean Optics. While bare bones and well known, it’s by no means cheap and the software is propriatary.
Consider the Spectruino, at only half a grand and with open source software. Have you tried the Spectruino? We’d love to know your thoughts.
The cheapest solution we know of is the DIY Desktop Spectrometry Kit from Public Lab. It even has a purchasable kit for just $50.
The EyeWriter is a DIY low-cost eye-tracking apparatus + custom software that allows people to draw using only their eyes. Eye tracking solutions generally cost upwards of ten grand, but this is just $200 in parts.
If your applying for grants, or just wondering who is using how much money for what, run some searches on Federal Reporter to understand the current state of American federal science funding.
An anonymous reader emailed us to share a small DIY microfluidic rig equipped with inexpensive board cameras. The chassis is mainly made out of laser-cut acrylic sheets, M6 nuts, and bolts. This GitHub page gives a comprehensive list of components complete with their cost, and instructions on how to assemble them.